Polyolefins, such as polyethylene and polypropylene-based films and nonwovens, have been widely used as structural components of disposable personal care products. Polyolefins provide many functional benefits, such as low cost, improved processibility, and a broad range of grades having tailored melt and solid state properties. Conventional polyolefins, however, are hydrophobic and do not provide a desired water responsive functionality.
Porous materials can be made by a variety of conventional techniques. For example, conventional phase separation methods have involved a mixing of a polymer resin with diluent or plasticizer, a quenching the polymer blend to induce phase separation, and a washing away of the diluent to leave a developed porous structure. The morphology of the porous structure can mainly depend on the type and amount of the diluent, the mixing efficiency and the washing technique. Other techniques have involved a multi-step stretching of polymer films, environmental crazing, and an addition of a blowing or swelling agent to create the microporous structure. Conventional techniques, such as those described above, however, have been limited in their ability to control the microporous morphology and the properties of the material. The techniques have also been unable to produce microporous films at a sufficiently high speed, and have not been adequately cost efficient for producing materials having desired physical and performance characteristics.
Porous films have been also made by incorporating filler particles into a polymer material and stretching the material to form a film with the voids induced by the filler. Technologies based upon the incorporation of filler particles introduces a range of variables, such as the type of filler, the amount of filler, the filler particle size and size distribution, any surface-modifications made to the filler particles, the mode or method of stretching the film, and the like. Each of these factors can affect the morphology and properties of the porous film.
Conventional porous films, such as those described above, have not been able to provide desired combinations of mechanical properties and water accessibility. In addition, the techniques have not adequately produced porous films having desired combinations of high wettability, high permeability to liquid, and high tensile strength. As a result, there has been a continuing need for polymer films, such as polyolefin-based films, having improved porous structures, such as porous films can have a microstructure which provides rapid water access into the material systems, can have high flexibility and low friction for flushability, and can have high strength, durability and softness to provided desired levels of in-use performance.